The invention relates to a method for detecting the position of a piston of a piston cylinder in which a microwave transmit signal is emitted in the direction of the piston and microwaves reflected from the piston are detected.
The invention further relates to an apparatus for measuring the position of a piston of a piston cylinder, said apparatus comprising a microwave transmitting device and a microwave receiving device which are at least partially arranged at the piston cylinder, wherein the microwave transmitting device emits transmit signals in the direction of the piston and the microwave receiving device receives and detects receive signals, and an evaluation device.
DE 20 2005 020 158 U1 discloses a measuring system for measuring the distance to a medium to be measured, said measuring system comprising a hollow conductor having a first end and a second end for conducting electromagnetic waves to the medium to be measured, a transmitter attachable to the first end for emitting a modulated electromagnetic wave into the hollow conductor, a receiver attachable to the first end for receiving electromagnetic waves coming from the hollow conductor, and an evaluation unit connected to the receiver for detecting the distance to the medium to be measured. Provided in the hollow conductor is a discontinuity which causes a defined portion of the electromagnetic wave guided in the hollow conductor to be reflected back to the receiver, and the evaluation unit is configured to detect the distance to the medium to be measured by comparing the electromagnetic wave reflected from the discontinuity with the electromagnetic wave reflected from the medium to be measured.
DE 10 2007 020 046 A1 discloses a method for determining a distance in which is provided a line structure having a reflective body, said line structure having a feed block with a feed region which connects an HF transceiver to the coupling probe via a waveguide with a dielectric holding system, and the reflective body has a base plate with a collar mounted thereon for forming a cup-shaped element. The distance between the feed point defined by the coupling probe and the reflective body is measured, wherein, via the coupling probe, at least two transmit signals are coupled in, preferably radiated and received, as electromagnetic waves having different frequencies.
DE 198 33 220 A1 discloses a distance measuring apparatus having a sensor device and evaluation electronics in which the sensor device has at least one coupling probe for feeding a transmit signal into a line structure.
U.S. Pat. No. 4,737,705 discloses a linear position sensor which uses a coaxial resonant cavity.
EP 0 303 595 B1 discloses an apparatus for detecting the linear position of a piston and a piston rod in which microwaves are reflected and transverse modes are generated.
The doctoral thesis entitled “Integrated Microwave Sensors for Cavity-Length Measurement in Machine Engineering” by Alexander Megej, published by Schaker Verlag, Aachen, 2002, describes microwave sensors which allow the length of a cylindrical cavity to be determined.